Again, some earlier code. I’m not sure how good this works…I had ran it for a few weeks awhile back. However, my IP address changed and I received a lot of notifications before I had a chance to resolve it. The script would be better if it contained some sort of logic so that it only sent one notification.
Monday, 08 October 2007
- The purpose of this script is to:
- lookup a domain name with nslookup, returning an IP address
- find the external network address translation (NAT) using whatismyip.org
- compare the two IP addresses
- send a notification if they are not the same
This script was designed to run as a scheduled task and in my scenario it runs every 30 minutes. The purpose is to work similiar to the www.no-ip.com service that will dynamically update DNS based on your external IP address. Since I do not typically have a scripting interface into my hosted external DNS, I use a simple CDO email to let me know when DNS needs to be manually updated.
NatName = "publicnat.domainname.com"
NotifyContact = " email@example.com"
smtpserver = "smtp.domainname.com"
IP_in_DNS = DNSLookup(NatName)
IP_on_OutSide = ExternalIP()
If Not IP_in_DNS = IP_on_OutSide Then
SendEmail NotifyContact,NatName & " issue","The network address translation for " & NatName & " (IP_" & IP_in_DNS & ") does not match the current external address of IP_" & IP_on_OutSide & "."
On error resume next
Const OpenAsDefault = -2
Const FailIfNotExist = 0
Const ForReading = 1
Set oShell = CreateObject("WScript.Shell")
Set oFSO = CreateObject("Scripting.FileSystemObject")
sTemp = oShell.ExpandEnvironmentStrings("%TEMP%")
sTempFile = sTemp & "\" & oFSO.GetTempName
oShell.Run "%comspec% /c nslookup " & sDNSName & ">" & sTempFile, 0, True
Set fFile = oFSO.OpenTextFile(sTempFile, ForReading, FailIfNotExist, OpenAsDefault)
sResults = fFile.ReadAll
If InStr(sResults, "Address:") Then
aNameTemp = Split(sResults, "Address:")
aName = Split(Trim(aNameTemp(2)), Chr(13))
'aNameTemp(2) will be the second address listed; the first address is that of the DNS Server
DNSLookup = aName(0)
DNSLookup = "Failed."
Set oShell = Nothing
Set oFSO = Nothing
url = "http://whatismyip.org"
set xmlhttp = CreateObject("MSXML2.ServerXMLHTTP")
xmlhttp.open "GET", url, false
ExternalIP = xmlhttp.responseText
set xmlhttp = Nothing
Sub SendEmail(strTo, strSubject, strBody)
Set objEmail = CreateObject("CDO.Message")
objEmail.From = NotifyContact
objEmail.To = strTo
objEmail.Subject = strSubject
objEmail.HTMLBody = strBody
("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
("http://schemas.microsoft.com/cdo/configuration/smtpserver") = smtpserver
("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25